Methodological development in NMR of a biomass analysis protocol by photo-CIDNP (Photo-Chemically Induced Dynamic Nuclear Polarization)
CONTEXT
The versatility of NMR for the analysis of complex biological mixtures has been described in recent years in the fields of health, food or plant sciences (1-3). These advantages have been highlighted in metabolomics, where NMR has contributed to the understanding of metabolic profiles by identifying and quantifying major components in the millimolar (mM) concentration range. (4)
However, minor compounds suffer from sensitivity limitations, intrinsic to NMR, overcome lately with the development of several hyperpolarization methods (5). Among them, the photo-Chemically Induced DNP (photo-CIDNP) method proves to be easy to implement on any NMR instrument and at a low cost. It is based on a radical pair mechanism between a metabolite and an excited photosensitizer, induced by light irradiation and takes place directly inside the spectrometer. Photo-CIDNP is effective when the target metabolite is highly conjugated, favoring the stabilization of the radical pair in the triplet state generated by the collision between the dye and the metabolite. For example, aromatic amino acids such as tyrosine, histidine or tryptophan and their derivatives can be observed in solution with an increase in the 1H signal between 100 and 400 times. (6)
Photo-CIDNP has rarely been used to date in metabolomics studies, which will involve the sequential analysis of a large number of samples.
OBJECTIVE
The objective of the internship is to develop a photo-CIDNP analysis method for natural products such as polyphenols, catechins or lignans, generally present in food products or biomass extracts.
Objectives of the internship:
Preliminary results have already been obtained in the laboratory, showing the interest of photo-CIDNP to improve the signal-to-noise ratio of catechins spectra by a factor of 10-20.
The objective of the internship is therefore:
- to optimize the analysis conditions in a model solution to assure a future possible sequential analysis of a large number of complex samples.
- these conditions could include: the type of photosensitizer (riboflavin or fluorescein); the initial concentration of the same; irradiation wavelength and duration; study of the stability of the photosensitizer; lifetime of the triplet state; etc.
- if necessary, optimization of the conditions for acquiring NMR data (pulse sequence, etc.).
- to validate the protocol developed with real complex mixtures such as commercial tea drinks or lignocellulosic biomass extract.
- to participate in discussions and/or laboratory meetings and the thematic group "Complex mixtures".
- to present his/her results at the end of the internship in the form of a report and an oral presentation.
Level/Training: 2nd year Master, end-of-year Master project
The student must have knowledge of analytical methods (mainly NMR) and the basics of physical chemistry (matter-light interaction). He/she may be required to work with colleagues from the Molecular Chemistry Laboratory (mass spectrometry analyses, etc.).
Location: Laboratoire de Chimie Moléculaire (LCM) at Ecole Polytechnique (Palaiseau, France); 25 km from the center of Paris (50 min by public transport).
The LCM of the Ecole Polytechnique has 2 spectrometers 300 MHz and a 400 MHz, with the future installation of a 600 MHz focused on light irradiation experiments. The student will work mainly with a 300 MHz Bruker Avance II, with a BBFO probe, which is connected to a light source with 5 different wavelengths between 360 and 650 nm.
Supervisor/additional Information:
Send CV, transcripts and cover letter to Covadonga Lucas-Torres (covadonga.lucas-torres@polytechnique.edu), Assistant Professor at the LCM.
And David Touboul, (david.touboul@cnrs.fr) CNRS Research Director at the LCM.
Period: from January 2025.
Funding: student grants are available.
References :
- Emwas et al, Metabolomics, 2013, 9, 1048. DOI: 10.1007/s11306-013-0524-y
2. Hatzakis, CRFSFS, 2019, 18, 189. DOI: 10.1111/1541-4337.12408
3. Deborde et al, Prog Nucl Magn Reson Spectrosc, 2017, 102, 61. DOI: 10.1016/j.pnmrs.2017.05.001
4. Nagana Gowda et al, Anal Chem, 2017, 89, 490. DOI: 10.1021/acs.analchem.6b04420
5. Ellis et al, Chem Rev, 2023, 123, 1417. DOI: 10.1021/acs.chemrev.2c00534
6. Torres et al, PCCP, 2021, 23, 6641. DOI: 10.1039/D0CP06068B